The moon rotates too slowly (about once every 30 days), you don’t want a space elevator for the moon, the tether would have to be ridiculously long.
But there’s no atmosphere, so you have another good option: a linear accelerator, or mass driver. Basically you make a very long, very straight rail and use electromagnetism to accelerate a craft right up to orbital velocity. The only complicated part is constructing 50 km of rail, but I mean, it’s more time consuming than complicated. This is actually way more feasible than a space elevator.
You still need to fire an engine on the far side of your orbit though which makes it more difficult as it still needs to be able to propel itself (while surviving the acceleration)
Well surviving the acceleration is trivial. I figured a 50km track in the post up above, in 50km you can accelerate up to lunar orbit velocities at just 1g of constant acceleration. So if your probe can survive sitting still on earth, it can survive accelerating at that speed.
You’re right though, you do need a small amount of thrust when you reach the top of your arc, but really not much. 50 m/s of DeltaV would do just fine. In other words, opening a can of compressed air would basically do it.
Or alternatively, you could use a mechanical system; you could have the vehicle (basically a rail cart) separate from the cargo with a powerful spring, pushing the cargo up, and the cart down. That mechanical system is also more effective the higher the apogee is, so if you launched the vehicle into a higher, more elliptical lunar orbit, that small push at the top pulls your low end of the orbit up much higher.
Ah, I was thinking more of a spinlaunch thing. Yours would make more sense, but would require a fuckton of industry in space or on the moon to have it work. I wonder how much more effective a self contained spinlaunch style thing would be on the moon.
Yeah, the application kind of assumes a lot of industry though. I mean if there isn’t a lot of industry, what are you shipping off the moon? But still, 50 km of rail is a lot, but it’s far less than the 325,000 km of tether that a space elevator would need…
Spin launch would definitely be feasible for some cargo, theoretically it would be a bit easier in vacuum, though that would probably also present other challenges. However, with a reasonably sized spin launch system (like the size of a 4 story apartment building), the payload needs to handle forces around 3000 Gs (which is a lot even for cargo). Unfortunately, you’d need to go larger for lower G force. So this also requires a lot of industry.
Wut? Impracticality aside, could they build such a “ridiculously long tether”? What’s they make it of? Musk farts? Can’t wait for him to bankrupt the u.s. and build a space elevator that breaks and shatters, ruining astronomy and prospects of drone explorations of Mars
Uh, well truth be told, you could probably use steel cable or carbon fiber for a lunar space elevator cable, but you would need some really insane quantities… Like I said, I wouldn’t recommend it, just go the mass driver route instead.
But why are you even bringing up Musk? Nobody is suggesting involving him…
Nah, it wouldn’t do much damage. The tether’s whole job is to be strong, but light. And being a long, thin fiber, it’ll have a pretty low mass to surface area ratio (high drag in atmo). If it did come down, it would likely mostly burn up, or mostly be slowed down by the atmosphere.
Additionally, the length of tether with the most tension on it will be the section nearest to the ground. If the tether snaps near the ground, the whole thing gets hauled up to orbit for good.
To be clear, I’m actually not in favor of space elevators in general, I think there are many much more practical ways to get to orbit. I’m just saying that a broken tether should not be the end of the world.
If you really want to build something like a space elevator though, you should check out the tethered ring concept: https://youtu.be/8B2iqiKehyM
The moon rotates too slowly (about once every 30 days), you don’t want a space elevator for the moon, the tether would have to be ridiculously long.
But there’s no atmosphere, so you have another good option: a linear accelerator, or mass driver. Basically you make a very long, very straight rail and use electromagnetism to accelerate a craft right up to orbital velocity. The only complicated part is constructing 50 km of rail, but I mean, it’s more time consuming than complicated. This is actually way more feasible than a space elevator.
You still need to fire an engine on the far side of your orbit though which makes it more difficult as it still needs to be able to propel itself (while surviving the acceleration)
Well surviving the acceleration is trivial. I figured a 50km track in the post up above, in 50km you can accelerate up to lunar orbit velocities at just 1g of constant acceleration. So if your probe can survive sitting still on earth, it can survive accelerating at that speed.
You’re right though, you do need a small amount of thrust when you reach the top of your arc, but really not much. 50 m/s of DeltaV would do just fine. In other words, opening a can of compressed air would basically do it.
Or alternatively, you could use a mechanical system; you could have the vehicle (basically a rail cart) separate from the cargo with a powerful spring, pushing the cargo up, and the cart down. That mechanical system is also more effective the higher the apogee is, so if you launched the vehicle into a higher, more elliptical lunar orbit, that small push at the top pulls your low end of the orbit up much higher.
Ah, I was thinking more of a spinlaunch thing. Yours would make more sense, but would require a fuckton of industry in space or on the moon to have it work. I wonder how much more effective a self contained spinlaunch style thing would be on the moon.
Yeah, the application kind of assumes a lot of industry though. I mean if there isn’t a lot of industry, what are you shipping off the moon? But still, 50 km of rail is a lot, but it’s far less than the 325,000 km of tether that a space elevator would need…
Spin launch would definitely be feasible for some cargo, theoretically it would be a bit easier in vacuum, though that would probably also present other challenges. However, with a reasonably sized spin launch system (like the size of a 4 story apartment building), the payload needs to handle forces around 3000 Gs (which is a lot even for cargo). Unfortunately, you’d need to go larger for lower G force. So this also requires a lot of industry.
Wut? Impracticality aside, could they build such a “ridiculously long tether”? What’s they make it of? Musk farts? Can’t wait for him to bankrupt the u.s. and build a space elevator that breaks and shatters, ruining astronomy and prospects of drone explorations of Mars
Uh, well truth be told, you could probably use steel cable or carbon fiber for a lunar space elevator cable, but you would need some really insane quantities… Like I said, I wouldn’t recommend it, just go the mass driver route instead.
But why are you even bringing up Musk? Nobody is suggesting involving him…
Space elevator breaking would be pretty catastrophic for a lot of earth when that shit falls.
Nah, it wouldn’t do much damage. The tether’s whole job is to be strong, but light. And being a long, thin fiber, it’ll have a pretty low mass to surface area ratio (high drag in atmo). If it did come down, it would likely mostly burn up, or mostly be slowed down by the atmosphere.
Additionally, the length of tether with the most tension on it will be the section nearest to the ground. If the tether snaps near the ground, the whole thing gets hauled up to orbit for good.
To be clear, I’m actually not in favor of space elevators in general, I think there are many much more practical ways to get to orbit. I’m just saying that a broken tether should not be the end of the world.
If you really want to build something like a space elevator though, you should check out the tethered ring concept: https://youtu.be/8B2iqiKehyM